JPH0759910B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel injection control device for injecting and supplying a fuel having an optimum air-fuel ratio to an internal combustion engine.

<Prior Art and Its Problems> As a conventional fuel injection control device for an internal combustion engine, there is one that measures an intake air amount using an air flow meter and injects fuel to an intake system of the engine in response to the measurement. well known.

However, in such a conventional fuel injection control device, the intake air amount changes during the time from the measurement of the intake air amount to the end of injection during a transition, particularly during acceleration, etc. There is a problem that the air-fuel ratio of the air-fuel mixture sucked into the air may become lean.

Further, as shown in JP-A-59-103965, JP-A-59-226254, JP-A-59-18867, JP-A-59-221433, etc., the pipe inside immediately after the intake valve is closed. There is a method in which the pressure is detected, the amount of air taken into the cylinder is calculated from this, and the fuel injection amount is controlled based on this.

However, in this one, although the fuel injection amount is calculated based on the air amount taken into the cylinder,
Since it is configured to be reflected in the next fuel injection, even if the amount of air taken into the cylinder can be accurately detected by the pipe internal pressure, the reflection will be shifted by one tempo, Also in this case, there is a problem in that the merit that the intake air amount to the cylinder can be accurately measured cannot be fully utilized in an excessive case.

The present invention has been made in view of the above conventional problems, and fuel injection control capable of responsively injecting and supplying an amount of fuel corresponding to the amount of air taken into the cylinder even in an emergency. The purpose is to provide a device.

<Means for Solving Problems> Therefore, according to the present invention, as shown in FIG. 1, an operating state detecting means a for detecting a parameter indicating an operating state of the engine.
A fuel injection amount calculation means b for calculating the fuel injection amount according to the detected parameter, a first fuel injection means c for injecting fuel to the engine based on the calculation result, and a cylinder near the end of the intake stroke. Cylinder intake air amount detecting means d for detecting the amount of air taken into the inside, and correction injection amount calculating means e for calculating the shortage of the fuel injection amount from the detected air amount.
And a second fuel injection means f for directly injecting fuel into the cylinder based on the result of this calculation, thereby forming a fuel injection control device.

<Operation> That is, while the means a to c perform fuel injection as in the conventional case, the means d detects the amount of air sucked into the cylinder near the end of the intake stroke, and the means e sucks air into the cylinder. The fuel injection amount corresponding to the fuel injection amount is subtracted from the fuel injection amount to obtain the shortage amount. If there is a shortage amount, the correction amount is used as the corrected injection amount and the means f directly injects and supplies it to each cylinder. The air-fuel mixture having the optimum air-fuel ratio is always supplied to

It should be noted that it is possible to think of detecting the amount of air taken into the cylinder near the end of the intake stroke and injecting the entire injection amount including the normal portion and the correction portion during the compression stroke by direct injection,
Even with this, it is possible to maintain the air-fuel ratio in the cylinder at the optimum value, but it is difficult in terms of time because the fuel injection must be completed during the compression stroke (actually, well before TDC). Even if the fuel can be injected, sufficient atomization cannot be expected and good combustion cannot be achieved. In this respect, in the present invention, only the correction is directly injected into the cylinder during the compression stroke, so the amount is small and the above-mentioned problems hardly occur.

<Embodiment> An embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 shows the system configuration of the fuel injection control device.

An air flow meter 1 is provided in the intake duct to measure the intake air flow rate Q and output a corresponding voltage signal.
Reference numeral 2 denotes a crank angle sensor, which outputs a reference pulse signal each time the crankshaft rotates a reference angle (for example, 180 ° C. in the case of four cylinders) and outputs a unit pulse signal each time the unit rotates by a unit angle (for example, 1 °). To do. The engine speed N can be calculated from these pulse signals. Therefore, the air flow meter 1 and the crank angle sensor 2 correspond to the operating condition detecting means for detecting the predetermined parameters (intake air flow rate Q and engine speed N in this example) representing the operating condition of the engine.

Reference numeral 3 denotes a pipe pressure sensor, which is provided for each cylinder. This is composed of a piezoelectric element PZ formed in a washer shape as shown in FIG. 3, for example, and is attached as a washer of the ignition plug IP on the cylinder head CH to generate an electric charge according to the pipe internal pressure. Reference numeral 4 denotes an amplifier, which is a pipe pressure sensor 3
A signal corresponding to the pipe pressure is output from the output of. this is,
For example, as shown in FIG. 4, resistors R _{1 to} R ₈ , a capacitor C,
The charge amplifier is a known charge-voltage generator including diodes D _{1 to} D ₃ and operational amplifiers OP ₁ and OP ₂ . An intake sensor 5 measures the intake air temperature in the intake manifold and outputs a corresponding voltage signal. Instead, a water temperature sensor that detects the cooling water temperature may be used. Here, the pipe pressure sensor 3, the amplifier 4 and the intake air temperature sensor 5 are provided as constituent elements of a cylinder intake air amount detecting means for detecting the amount of air taken into the cylinder near the end of the intake stroke.

Reference numeral 6 denotes a microcomputer unit, which comprises an I / O port 61, CPU62, ROM63, RAM64, A / D converter 65, etc. The signals of various sensors are A / D converted as necessary and read, and predetermined arithmetic processing is performed. The microcomputer unit 6 constitutes fuel injection calculation means and corrected injection amount calculation means.

Reference numeral 7 denotes a main fuel injection device as a first fuel injection means, which injects and supplies an amount of fuel calculated according to an operating state to the engine intake system based on a command from the microcomputer unit 6. One of these may be provided at the collecting portion of the intake manifold, or may be provided for each cylinder at the branch portion of the intake manifold or the intake port.

Reference numeral 8 denotes an in-cylinder direct fuel injection device as a second fuel injection means, which is provided for each cylinder and is calculated based on the command of the microcomputer unit 6 and the amount of air taken into the cylinder. Insufficient amount of fuel injection amount to be injected is directly supplied into the cylinder.

Next, the arithmetic processing by the microcomputer unit 6 will be described in accordance with the programs shown in FIGS.

In step 1 of the program of FIG. 5 (denoted as S1 in the figure; the same applies hereinafter), the intake air flow rate Q is detected based on the signal from the air flow meter 1, and in step 2, the signal from the crank angle sensor 2 is detected. The engine speed N is calculated based on

Next, at step 3, the basic fuel injection amount Tp = K · Q / N (K is a constant) is calculated from the intake air flow rate Q and the engine speed N. Then, in step 4, the fuel injection amount Ti = Tp · COEF is calculated by making corrections using various correction coefficients COEF and the like. This portion corresponds to the fuel injection amount calculation means.

Next, in step 5, driving with a pulse width corresponding to the fuel injection amount Ti is performed at a predetermined timing synchronized with the engine rotation (when fuel injection is performed for each cylinder, injection is ended before the end of the intake stroke). A pulse signal is output to the main fuel injection device 7 to perform normal fuel injection.

The program of FIG. 6 is started based on a signal from the crank angle sensor 2 at the end of the intake stroke of each cylinder (immediately after the intake valve is closed).

First, at step 11, the signal output from the in-cylinder pressure sensor 3 via the amplifier 4 is A / D converted and read to read the in-cylinder pressure at the end of the intake stroke (that is, the pressure of the air actually sucked into the cylinder). Pa is detected, and in step 12, the signal from the intake air temperature sensor 5 is A / D converted and read to detect the intake air temperature Ta.

Next, at step 13, the air amount (mass) Ac sucked into the cylinder is calculated from the in-cylinder pressure Pa and the intake air temperature Ta. As this method, for example, what is experimentally obtained in advance may be stored in the ROM 63 in the form of a table (map), and the ROM 63 may be searched. This portion, together with the in-cylinder pressure sensor 3, the amplifier 4, and the intake air temperature sensor 5, corresponds to cylinder intake air amount detection means.

Next, in step 14, the cylinder intake air amount Ac obtained in step 13 is compared with the fuel injection amount Ti injected by the main fuel injection device 7, and when the ratio is larger than the optimum value, that is, the cylinder is compared with the fuel injection amount Ti. When the intake air amount Ac is large,
Go to next step 15. Otherwise, exit this program.

In step 15, the injected fuel injection amount Ti is subtracted from the appropriate fuel injection amount C · Ac calculated by multiplying the cylinder intake air amount Ac by a predetermined coefficient C, and the insufficient correction injection amount ΔTi
Is calculated. This portion corresponds to the corrected injection amount calculation means.

Then, in step 16, a drive pulse signal having a pulse width corresponding to this corrected injection amount ΔTi is output to the in-cylinder direct fuel injection device 8 of the corresponding cylinder to directly inject fuel into the cylinder during the compression stroke after the intake stroke. Inject it. In this way, an appropriate air-fuel ratio is always secured.

In this embodiment, no countermeasure is taken when the fuel injection amount by the main fuel injection device 7 is too large. However, for this purpose, for example, the amount injected by the main fuel injection device 7 is made small. In addition, the in-cylinder direct fuel injection device 8 may increase or decrease the corrected injection amount including the small amount. In this case, the direct cylinder fuel injection device 8
As a result, fuel injection is performed steadily, and by utilizing this, a region of combustible air-fuel mixture may be formed near the spark plug to perform lean combustion.

Further, the main fuel injection device 7 may also directly inject fuel into the cylinder, and in this case, the main fuel injection device 7 may also serve as the in-cylinder direct fuel injection device 8 for cost reduction. it can. In other words, the main injection is performed during the intake stroke, and the correction injection is performed immediately after calculation after the intake valve is closed, so that it is possible to supply good atomized fuel even by direct injection alone, and to perform all after the intake valve is closed. Better results than spraying.

Further, the air flow meter 1 for detecting the operating state of the engine may be replaced with the cylinder pressure sensor 3 and the intake air temperature sensor 5 without using it. That is, the basic fuel injection amount may be calculated based on the information of the cylinder that injected the previous fuel.

Also, to detect the amount of air taken into the cylinder,
Although the in-cylinder pressure sensor 3 is used, a negative pressure sensor that detects a negative pressure in the intake manifold is used, and the cylinder intake air amount is calculated from the intake pipe negative pressure and intake temperature (or cooling water temperature) immediately before the intake valve is closed. May be requested.

<Effects of the Invention> As described above, according to the present invention, it is possible to obtain the effect that the mixture that is always optimum and sufficiently atomized with respect to the amount of air sucked into the cylinder can be supplied.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system configuration diagram of a fuel injection control device showing an embodiment of the present invention, and FIG. 3 is a diagram showing a specific example of a cylinder pressure sensor, Fourth
The figure shows a concrete sequence of the amplifier, and FIGS. 5 and 6 are flowcharts showing the control program. 1 ... Air flow meter, 2 ... Crank angle sensor, 3
...... Cylinder pressure sensor, 4 ... Amplifier, 5 ... Intake air temperature sensor, 6 ... Microcomputer unit, 7 ... Main fuel injection device, 8 ... Cylinder direct fuel injection device

Claims (1)

[Claims] 1. An operating condition detecting means for detecting a predetermined parameter representing an operating condition of the engine, and a fuel injection amount calculating means for calculating a fuel injection amount according to the detected parameter.
The first fuel injection means for injecting fuel into the engine based on the result of this calculation, the cylinder intake air amount detection means for detecting the amount of air taken into the cylinder near the end of the intake stroke, and the detected air amount A fuel injection control device for an internal combustion engine, comprising: a correction injection amount calculation means for calculating a shortage of a fuel injection amount; and a second fuel injection means for directly injecting fuel into a cylinder based on the calculation result.